Investigating relationships between Teleconnections around the Mediterranean and
their influence on aerosol transport using a Regional Climate Model (RegCM4)
James M. Ciarlo`*, Noel J. Aquilina
*Contact e-mail – jcia0004@um.edu.mt
Department of Physics, Faculty of Science, University of Malta
1. Introduction
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Atmospheric processes are strongly influenced by teleconnections such as the North Atlantic Oscillation (NAO) [1; 2; 3].
Teleconnection patterns depend on the atmospheric pressure at two distant locations, and thus, strongly influence wind vectors [3; 4; 5].
Circulation around the Mediterranean region contains various teleconnections, in particular the following sea level pressure (SLP) patterns:
NAO (a), Southern Europe-North Atlantic (SENA) Pattern (b) [6], Western Mediterranean Oscillation (WeMO)(c) [7], and the Central AfricanCaspian Oscillation (CACO)(d) [5].
This research also included teleconnections based on other pressure levels. These included the following: East Atlantic (EA) pattern [8],
Scandinavian (SCA) pattern [8], Eastern Atlantic-Western Russia (EAWR) pattern [8], Mediterranean Oscillation (MO) [9], and North SeaCaspian Pattern (NCP) [4].
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The target of this study was to investigate if such a number of circulation phenomena clustered together around a relatively small area,
are likely to experience a certain level of interaction with each other, as well as influence aerosol transport in and out of the region.
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For this project, a simulation was conducted using RegCM4.0 for the time period of 1983-2009. This simulation, together with data from
NCEP/NCAR Reanalysis Monthly Means (available from: http://www.esrl.noaa.gov/psd/data/gridded/data.ncep.reanalysis.derived.html), was
used to assess the use of the RegCM4.0 model for the calculation of oscillation indices and analyze the two above-mentioned hypotheses.
2. Teleconnections in RegCM4
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By correlating the RegCM4.0 derived indices with the NCEP/NCAR Reanalysis derived
indices the quality of the data obtained from RegCM4.0 is revealed.
Correlation Coefficient
All results were statistically significant to the 0.01 level
Most reliable data from: EA, NAO, SCA, & SENA indices
Least reliable data from: CACO index – low correlation & gradient – least reliable data
CACO
EA
EAWR
MO
NAO
NCP
SCA
SENA
WeMO
0.351
0.925
0.659
0.598
0.889
0.619
0.747
0.826
0.504
3. Inter-Pattern Relationships
Since the influence of teleconnection patterns extends over great distances, and the patterns
being studied are relatively close together, interaction is inevitable.
EA
EAWR
MO
NAO
NCP
SCA
SENA
WeMO
CACO
-0.089
0.031
-0.117
-0.109
-0.127
0.036
-0.295
0.443
EA
-
-0.295
0.400
0.514
-0.120
-0.216
-0.372
-0.010
-
0.197
0.027
0.937
-0.017
0.287
-0.566
-
0.266
0.305
-0.454
0.476
-0.545
-
0.167
-0.165
0.865
-0.100
-
0.015
0.427
-0.657
-
-0.302
0.324
-
-0.563
By producing correlation fields of the indices with pressure fields a map of the influence of the
teleconnection is obtained (shown below).
EAWR
However, correlating the teleconnection indices gives quantitative data as results (shown right).
NAO
MO
NCP
SCA
Significant to the 0.05 level
SENA
Significant to the 0.01 level
The results indicate a strong positive relationship between NCP and EAWR which may represent
the same teleconnection as suggested by Kutiel & Benaroch [2002], and between NAO and SENA
possibly due to the same inferences.
For the remaining teleconnections, interactive behavior rarely exceeds a coefficient of 0.6.
4. Influence on Dust
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Temporal correlation was performed between the teleconnection indices and the
wind components, thus producing the vector fields displayed (top) as well as temporal
correlation between indices and dust concentration (bottom).
The results indicate a similar influence for NAO, SENA and MO (right). During the
positive phase these teleconnections, transport aerosol dust from the Mediterranean
and Black Sea areas towards western Africa and then north-bound to Continental
Europe. During a negative phase this is reversed.
The results for NCP (below) are similar to NAO, SENA and MO, however, have an
increased influence over Scandinavia. While the results for the CACO appear opposite
to the rest, resulting in a negative relationship over all of Continental Europe and a
positive relationship mostly east of the Caspian Sea.
5. References
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2.
3.
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6.
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This study reveals that it is possible to use teleconnections as a means of mapping
aerosol transport. Therefore it may be also possible to use regional climate model
simulations and teleconnections indices to project future aerosol transport.
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9.
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